In a two-line braking system, what is the effect of a rupture in the emergency line to the trailer?

In a two-line braking system for trucks with trailers, there are two air lines: the service line (controls normal braking) and the emergency line (provides air supply and activates emergency brakes if a problem occurs). If the emergency line ruptures, the air pressure drops, causing the trailer’s brakes to apply automatically—this is a safety measure to stop the trailer if it becomes separated or if there’s a pressure loss. Additionally, a valve seals off the trailer’s air supply from the broken emergency line to prevent a total air loss. That’s why both answer 1 (causes the trailer to brake) and answer 2 (seals off the trailer air supply from the broken emergency line) are correct. This setup helps prevent runaways and ensures the trailer stops safely in case of a malfunction.